diff options
Diffstat (limited to 'Lib/inspect.py')
| -rw-r--r-- | Lib/inspect.py | 775 |
1 files changed, 772 insertions, 3 deletions
diff --git a/Lib/inspect.py b/Lib/inspect.py index c3338f24..484c9c3 100644 --- a/Lib/inspect.py +++ b/Lib/inspect.py @@ -22,12 +22,14 @@ Here are some of the useful functions provided by this module: getouterframes(), getinnerframes() - get info about frames currentframe() - get the current stack frame stack(), trace() - get info about frames on the stack or in a traceback + + signature() - get a Signature object for the callable """ # This module is in the public domain. No warranties. -__author__ = 'Ka-Ping Yee <ping@lfw.org>' -__date__ = '1 Jan 2001' +__author__ = ('Ka-Ping Yee <ping@lfw.org>', + 'Yury Selivanov <yselivanov@sprymix.com>') import imp import importlib.machinery @@ -39,8 +41,9 @@ import sys import tokenize import types import warnings +import functools from operator import attrgetter -from collections import namedtuple +from collections import namedtuple, OrderedDict # Create constants for the compiler flags in Include/code.h # We try to get them from dis to avoid duplication, but fall @@ -1223,3 +1226,769 @@ def getgeneratorstate(generator): if generator.gi_frame.f_lasti == -1: return GEN_CREATED return GEN_SUSPENDED + + +############################################################################### +### Function Signature Object (PEP 362) +############################################################################### + + +_WrapperDescriptor = type(type.__call__) +_MethodWrapper = type(all.__call__) + +_NonUserDefinedCallables = (_WrapperDescriptor, + _MethodWrapper, + types.BuiltinFunctionType) + + +def _get_user_defined_method(cls, method_name): + try: + meth = getattr(cls, method_name) + except AttributeError: + return + else: + if not isinstance(meth, _NonUserDefinedCallables): + # Once '__signature__' will be added to 'C'-level + # callables, this check won't be necessary + return meth + + +def signature(obj): + '''Get a signature object for the passed callable.''' + + if not callable(obj): + raise TypeError('{!r} is not a callable object'.format(obj)) + + if isinstance(obj, types.MethodType): + # In this case we skip the first parameter of the underlying + # function (usually `self` or `cls`). + sig = signature(obj.__func__) + return sig.replace(parameters=tuple(sig.parameters.values())[1:]) + + try: + sig = obj.__signature__ + except AttributeError: + pass + else: + if sig is not None: + return sig + + try: + # Was this function wrapped by a decorator? + wrapped = obj.__wrapped__ + except AttributeError: + pass + else: + return signature(wrapped) + + if isinstance(obj, types.FunctionType): + return Signature.from_function(obj) + + if isinstance(obj, functools.partial): + sig = signature(obj.func) + + new_params = OrderedDict(sig.parameters.items()) + + partial_args = obj.args or () + partial_keywords = obj.keywords or {} + try: + ba = sig.bind_partial(*partial_args, **partial_keywords) + except TypeError as ex: + msg = 'partial object {!r} has incorrect arguments'.format(obj) + raise ValueError(msg) from ex + + for arg_name, arg_value in ba.arguments.items(): + param = new_params[arg_name] + if arg_name in partial_keywords: + # We set a new default value, because the following code + # is correct: + # + # >>> def foo(a): print(a) + # >>> print(partial(partial(foo, a=10), a=20)()) + # 20 + # >>> print(partial(partial(foo, a=10), a=20)(a=30)) + # 30 + # + # So, with 'partial' objects, passing a keyword argument is + # like setting a new default value for the corresponding + # parameter + # + # We also mark this parameter with '_partial_kwarg' + # flag. Later, in '_bind', the 'default' value of this + # parameter will be added to 'kwargs', to simulate + # the 'functools.partial' real call. + new_params[arg_name] = param.replace(default=arg_value, + _partial_kwarg=True) + + elif (param.kind not in (_VAR_KEYWORD, _VAR_POSITIONAL) and + not param._partial_kwarg): + new_params.pop(arg_name) + + return sig.replace(parameters=new_params.values()) + + sig = None + if isinstance(obj, type): + # obj is a class or a metaclass + + # First, let's see if it has an overloaded __call__ defined + # in its metaclass + call = _get_user_defined_method(type(obj), '__call__') + if call is not None: + sig = signature(call) + else: + # Now we check if the 'obj' class has a '__new__' method + new = _get_user_defined_method(obj, '__new__') + if new is not None: + sig = signature(new) + else: + # Finally, we should have at least __init__ implemented + init = _get_user_defined_method(obj, '__init__') + if init is not None: + sig = signature(init) + elif not isinstance(obj, _NonUserDefinedCallables): + # An object with __call__ + # We also check that the 'obj' is not an instance of + # _WrapperDescriptor or _MethodWrapper to avoid + # infinite recursion (and even potential segfault) + call = _get_user_defined_method(type(obj), '__call__') + if call is not None: + sig = signature(call) + + if sig is not None: + # For classes and objects we skip the first parameter of their + # __call__, __new__, or __init__ methods + return sig.replace(parameters=tuple(sig.parameters.values())[1:]) + + if isinstance(obj, types.BuiltinFunctionType): + # Raise a nicer error message for builtins + msg = 'no signature found for builtin function {!r}'.format(obj) + raise ValueError(msg) + + raise ValueError('callable {!r} is not supported by signature'.format(obj)) + + +class _void: + '''A private marker - used in Parameter & Signature''' + + +class _empty: + pass + + +class _ParameterKind(int): + def __new__(self, *args, name): + obj = int.__new__(self, *args) + obj._name = name + return obj + + def __str__(self): + return self._name + + def __repr__(self): + return '<_ParameterKind: {!r}>'.format(self._name) + + +_POSITIONAL_ONLY = _ParameterKind(0, name='POSITIONAL_ONLY') +_POSITIONAL_OR_KEYWORD = _ParameterKind(1, name='POSITIONAL_OR_KEYWORD') +_VAR_POSITIONAL = _ParameterKind(2, name='VAR_POSITIONAL') +_KEYWORD_ONLY = _ParameterKind(3, name='KEYWORD_ONLY') +_VAR_KEYWORD = _ParameterKind(4, name='VAR_KEYWORD') + + +class Parameter: + '''Represents a parameter in a function signature. + + Has the following public attributes: + + * name : str + The name of the parameter as a string. + * default : object + The default value for the parameter if specified. If the + parameter has no default value, this attribute is not set. + * annotation + The annotation for the parameter if specified. If the + parameter has no annotation, this attribute is not set. + * kind : str + Describes how argument values are bound to the parameter. + Possible values: `Parameter.POSITIONAL_ONLY`, + `Parameter.POSITIONAL_OR_KEYWORD`, `Parameter.VAR_POSITIONAL`, + `Parameter.KEYWORD_ONLY`, `Parameter.VAR_KEYWORD`. + ''' + + __slots__ = ('_name', '_kind', '_default', '_annotation', '_partial_kwarg') + + POSITIONAL_ONLY = _POSITIONAL_ONLY + POSITIONAL_OR_KEYWORD = _POSITIONAL_OR_KEYWORD + VAR_POSITIONAL = _VAR_POSITIONAL + KEYWORD_ONLY = _KEYWORD_ONLY + VAR_KEYWORD = _VAR_KEYWORD + + empty = _empty + + def __init__(self, name, kind, *, default=_empty, annotation=_empty, + _partial_kwarg=False): + + if kind not in (_POSITIONAL_ONLY, _POSITIONAL_OR_KEYWORD, + _VAR_POSITIONAL, _KEYWORD_ONLY, _VAR_KEYWORD): + raise ValueError("invalid value for 'Parameter.kind' attribute") + self._kind = kind + + if default is not _empty: + if kind in (_VAR_POSITIONAL, _VAR_KEYWORD): + msg = '{} parameters cannot have default values'.format(kind) + raise ValueError(msg) + self._default = default + self._annotation = annotation + + if name is None: + if kind != _POSITIONAL_ONLY: + raise ValueError("None is not a valid name for a " + "non-positional-only parameter") + self._name = name + else: + name = str(name) + if kind != _POSITIONAL_ONLY and not name.isidentifier(): + msg = '{!r} is not a valid parameter name'.format(name) + raise ValueError(msg) + self._name = name + + self._partial_kwarg = _partial_kwarg + + @property + def name(self): + return self._name + + @property + def default(self): + return self._default + + @property + def annotation(self): + return self._annotation + + @property + def kind(self): + return self._kind + + def replace(self, *, name=_void, kind=_void, annotation=_void, + default=_void, _partial_kwarg=_void): + '''Creates a customized copy of the Parameter.''' + + if name is _void: + name = self._name + + if kind is _void: + kind = self._kind + + if annotation is _void: + annotation = self._annotation + + if default is _void: + default = self._default + + if _partial_kwarg is _void: + _partial_kwarg = self._partial_kwarg + + return type(self)(name, kind, default=default, annotation=annotation, + _partial_kwarg=_partial_kwarg) + + def __str__(self): + kind = self.kind + + formatted = self._name + if kind == _POSITIONAL_ONLY: + if formatted is None: + formatted = '' + formatted = '<{}>'.format(formatted) + + # Add annotation and default value + if self._annotation is not _empty: + formatted = '{}:{}'.format(formatted, + formatannotation(self._annotation)) + + if self._default is not _empty: + formatted = '{}={}'.format(formatted, repr(self._default)) + + if kind == _VAR_POSITIONAL: + formatted = '*' + formatted + elif kind == _VAR_KEYWORD: + formatted = '**' + formatted + + return formatted + + def __repr__(self): + return '<{} at {:#x} {!r}>'.format(self.__class__.__name__, + id(self), self.name) + + def __eq__(self, other): + return (issubclass(other.__class__, Parameter) and + self._name == other._name and + self._kind == other._kind and + self._default == other._default and + self._annotation == other._annotation) + + def __ne__(self, other): + return not self.__eq__(other) + + +class BoundArguments: + '''Result of `Signature.bind` call. Holds the mapping of arguments + to the function's parameters. + + Has the following public attributes: + + * arguments : OrderedDict + An ordered mutable mapping of parameters' names to arguments' values. + Does not contain arguments' default values. + * signature : Signature + The Signature object that created this instance. + * args : tuple + Tuple of positional arguments values. + * kwargs : dict + Dict of keyword arguments values. + ''' + + def __init__(self, signature, arguments): + self.arguments = arguments + self._signature = signature + + @property + def signature(self): + return self._signature + + @property + def args(self): + args = [] + for param_name, param in self._signature.parameters.items(): + if (param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY) or + param._partial_kwarg): + # Keyword arguments mapped by 'functools.partial' + # (Parameter._partial_kwarg is True) are mapped + # in 'BoundArguments.kwargs', along with VAR_KEYWORD & + # KEYWORD_ONLY + break + + try: + arg = self.arguments[param_name] + except KeyError: + # We're done here. Other arguments + # will be mapped in 'BoundArguments.kwargs' + break + else: + if param.kind == _VAR_POSITIONAL: + # *args + args.extend(arg) + else: + # plain argument + args.append(arg) + + return tuple(args) + + @property + def kwargs(self): + kwargs = {} + kwargs_started = False + for param_name, param in self._signature.parameters.items(): + if not kwargs_started: + if (param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY) or + param._partial_kwarg): + kwargs_started = True + else: + if param_name not in self.arguments: + kwargs_started = True + continue + + if not kwargs_started: + continue + + try: + arg = self.arguments[param_name] + except KeyError: + pass + else: + if param.kind == _VAR_KEYWORD: + # **kwargs + kwargs.update(arg) + else: + # plain keyword argument + kwargs[param_name] = arg + + return kwargs + + def __eq__(self, other): + return (issubclass(other.__class__, BoundArguments) and + self.signature == other.signature and + self.arguments == other.arguments) + + def __ne__(self, other): + return not self.__eq__(other) + + +class Signature: + '''A Signature object represents the overall signature of a function. + It stores a Parameter object for each parameter accepted by the + function, as well as information specific to the function itself. + + A Signature object has the following public attributes and methods: + + * parameters : OrderedDict + An ordered mapping of parameters' names to the corresponding + Parameter objects (keyword-only arguments are in the same order + as listed in `code.co_varnames`). + * return_annotation : object + The annotation for the return type of the function if specified. + If the function has no annotation for its return type, this + attribute is not set. + * bind(*args, **kwargs) -> BoundArguments + Creates a mapping from positional and keyword arguments to + parameters. + * bind_partial(*args, **kwargs) -> BoundArguments + Creates a partial mapping from positional and keyword arguments + to parameters (simulating 'functools.partial' behavior.) + ''' + + __slots__ = ('_return_annotation', '_parameters') + + _parameter_cls = Parameter + _bound_arguments_cls = BoundArguments + + empty = _empty + + def __init__(self, parameters=None, *, return_annotation=_empty, + __validate_parameters__=True): + '''Constructs Signature from the given list of Parameter + objects and 'return_annotation'. All arguments are optional. + ''' + + if parameters is None: + params = OrderedDict() + else: + if __validate_parameters__: + params = OrderedDict() + top_kind = _POSITIONAL_ONLY + + for idx, param in enumerate(parameters): + kind = param.kind + if kind < top_kind: + msg = 'wrong parameter order: {} before {}' + msg = msg.format(top_kind, param.kind) + raise ValueError(msg) + else: + top_kind = kind + + name = param.name + if name is None: + name = str(idx) + param = param.replace(name=name) + + if name in params: + msg = 'duplicate parameter name: {!r}'.format(name) + raise ValueError(msg) + params[name] = param + else: + params = OrderedDict(((param.name, param) + for param in parameters)) + + self._parameters = types.MappingProxyType(params) + self._return_annotation = return_annotation + + @classmethod + def from_function(cls, func): + '''Constructs Signature for the given python function''' + + if not isinstance(func, types.FunctionType): + raise TypeError('{!r} is not a Python function'.format(func)) + + Parameter = cls._parameter_cls + + # Parameter information. + func_code = func.__code__ + pos_count = func_code.co_argcount + arg_names = func_code.co_varnames + positional = tuple(arg_names[:pos_count]) + keyword_only_count = func_code.co_kwonlyargcount + keyword_only = arg_names[pos_count:(pos_count + keyword_only_count)] + annotations = func.__annotations__ + defaults = func.__defaults__ + kwdefaults = func.__kwdefaults__ + + if defaults: + pos_default_count = len(defaults) + else: + pos_default_count = 0 + + parameters = [] + + # Non-keyword-only parameters w/o defaults. + non_default_count = pos_count - pos_default_count + for name in positional[:non_default_count]: + annotation = annotations.get(name, _empty) + parameters.append(Parameter(name, annotation=annotation, + kind=_POSITIONAL_OR_KEYWORD)) + + # ... w/ defaults. + for offset, name in enumerate(positional[non_default_count:]): + annotation = annotations.get(name, _empty) + parameters.append(Parameter(name, annotation=annotation, + kind=_POSITIONAL_OR_KEYWORD, + default=defaults[offset])) + + # *args + if func_code.co_flags & 0x04: + name = arg_names[pos_count + keyword_only_count] + annotation = annotations.get(name, _empty) + parameters.append(Parameter(name, annotation=annotation, + kind=_VAR_POSITIONAL)) + + # Keyword-only parameters. + for name in keyword_only: + default = _empty + if kwdefaults is not None: + default = kwdefaults.get(name, _empty) + + annotation = annotations.get(name, _empty) + parameters.append(Parameter(name, annotation=annotation, + kind=_KEYWORD_ONLY, + default=default)) + # **kwargs + if func_code.co_flags & 0x08: + index = pos_count + keyword_only_count + if func_code.co_flags & 0x04: + index += 1 + + name = arg_names[index] + annotation = annotations.get(name, _empty) + parameters.append(Parameter(name, annotation=annotation, + kind=_VAR_KEYWORD)) + + return cls(parameters, + return_annotation=annotations.get('return', _empty), + __validate_parameters__=False) + + @property + def parameters(self): + return self._parameters + + @property + def return_annotation(self): + return self._return_annotation + + def replace(self, *, parameters=_void, return_annotation=_void): + '''Creates a customized copy of the Signature. + Pass 'parameters' and/or 'return_annotation' arguments + to override them in the new copy. + ''' + + if parameters is _void: + parameters = self.parameters.values() + + if return_annotation is _void: + return_annotation = self._return_annotation + + return type(self)(parameters, + return_annotation=return_annotation) + + def __eq__(self, other): + if (not issubclass(type(other), Signature) or + self.return_annotation != other.return_annotation or + len(self.parameters) != len(other.parameters)): + return False + + other_positions = {param: idx + for idx, param in enumerate(other.parameters.keys())} + + for idx, (param_name, param) in enumerate(self.parameters.items()): + if param.kind == _KEYWORD_ONLY: + try: + other_param = other.parameters[param_name] + except KeyError: + return False + else: + if param != other_param: + return False + else: + try: + other_idx = other_positions[param_name] + except KeyError: + return False + else: + if (idx != other_idx or + param != other.parameters[param_name]): + return False + + return True + + def __ne__(self, other): + return not self.__eq__(other) + + def _bind(self, args, kwargs, *, partial=False): + '''Private method. Don't use directly.''' + + arguments = OrderedDict() + + parameters = iter(self.parameters.values()) + parameters_ex = () + arg_vals = iter(args) + + if partial: + # Support for binding arguments to 'functools.partial' objects. + # See 'functools.partial' case in 'signature()' implementation + # for details. + for param_name, param in self.parameters.items(): + if (param._partial_kwarg and param_name not in kwargs): + # Simulating 'functools.partial' behavior + kwargs[param_name] = param.default + + while True: + # Let's iterate through the positional arguments and corresponding + # parameters + try: + arg_val = next(arg_vals) + except StopIteration: + # No more positional arguments + try: + param = next(parameters) + except StopIteration: + # No more parameters. That's it. Just need to check that + # we have no `kwargs` after this while loop + break + else: + if param.kind == _VAR_POSITIONAL: + # That's OK, just empty *args. Let's start parsing + # kwargs + break + elif param.name in kwargs: + if param.kind == _POSITIONAL_ONLY: + msg = '{arg!r} parameter is positional only, ' \ + 'but was passed as a keyword' + msg = msg.format(arg=param.name) + raise TypeError(msg) from None + parameters_ex = (param,) + break + elif (param.kind == _VAR_KEYWORD or + param.default is not _empty): + # That's fine too - we have a default value for this + # parameter. So, lets start parsing `kwargs`, starting + # with the current parameter + parameters_ex = (param,) + break + else: + if partial: + parameters_ex = (param,) + break + else: + msg = '{arg!r} parameter lacking default value' + msg = msg.format(arg=param.name) + raise TypeError(msg) from None + else: + # We have a positional argument to process + try: + param = next(parameters) + except StopIteration: + raise TypeError('too many positional arguments') from None + else: + if param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY): + # Looks like we have no parameter for this positional + # argument + raise TypeError('too many positional arguments') + + if param.kind == _VAR_POSITIONAL: + # We have an '*args'-like argument, let's fill it with + # all positional arguments we have left and move on to + # the next phase + values = [arg_val] + values.extend(arg_vals) + arguments[param.name] = tuple(values) + break + + if param.name in kwargs: + raise TypeError('multiple values for argument ' + '{arg!r}'.format(arg=param.name)) + + arguments[param.name] = arg_val + + # Now, we iterate through the remaining parameters to process + # keyword arguments + kwargs_param = None + for param in itertools.chain(parameters_ex, parameters): + if param.kind == _POSITIONAL_ONLY: + # This should never happen in case of a properly built + # Signature object (but let's have this check here + # to ensure correct behaviour just in case) + raise TypeError('{arg!r} parameter is positional only, ' + 'but was passed as a keyword'. \ + format(arg=param.name)) + + if param.kind == _VAR_KEYWORD: + # Memorize that we have a '**kwargs'-like parameter + kwargs_param = param + continue + + param_name = param.name + try: + arg_val = kwargs.pop(param_name) + except KeyError: + # We have no value for this parameter. It's fine though, + # if it has a default value, or it is an '*args'-like + # parameter, left alone by the processing of positional + # arguments. + if (not partial and param.kind != _VAR_POSITIONAL and + param.default is _empty): + raise TypeError('{arg!r} parameter lacking default value'. \ + format(arg=param_name)) from None + + else: + arguments[param_name] = arg_val + + if kwargs: + if kwargs_param is not None: + # Process our '**kwargs'-like parameter + arguments[kwargs_param.name] = kwargs + else: + raise TypeError('too many keyword arguments') + + return self._bound_arguments_cls(self, arguments) + + def bind(self, *args, **kwargs): + '''Get a BoundArguments object, that maps the passed `args` + and `kwargs` to the function's signature. Raises `TypeError` + if the passed arguments can not be bound. + ''' + return self._bind(args, kwargs) + + def bind_partial(self, *args, **kwargs): + '''Get a BoundArguments object, that partially maps the + passed `args` and `kwargs` to the function's signature. + Raises `TypeError` if the passed arguments can not be bound. + ''' + return self._bind(args, kwargs, partial=True) + + def __str__(self): + result = [] + render_kw_only_separator = True + for idx, param in enumerate(self.parameters.values()): + formatted = str(param) + + kind = param.kind + if kind == _VAR_POSITIONAL: + # OK, we have an '*args'-like parameter, so we won't need + # a '*' to separate keyword-only arguments + render_kw_only_separator = False + elif kind == _KEYWORD_ONLY and render_kw_only_separator: + # We have a keyword-only parameter to render and we haven't + # rendered an '*args'-like parameter before, so add a '*' + # separator to the parameters list ("foo(arg1, *, arg2)" case) + result.append('*') + # This condition should be only triggered once, so + # reset the flag + render_kw_only_separator = False + + result.append(formatted) + + rendered = '({})'.format(', '.join(result)) + + if self.return_annotation is not _empty: + anno = formatannotation(self.return_annotation) + rendered += ' -> {}'.format(anno) + + return rendered |